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Re: Are you trying to start a mushroom farm in your attic? Posted by Snowmobile [Email]  (#686)  [Profile/Gallery]
(more from Snowmobile) on Wed, 19 Feb 2014 03:32:02
In Reply to: Re: Are you trying to start a mushroom farm in your attic?, AdamSAAB2kAero  [Profile/Gallery]
, Tue, 18 Feb 2014 16:28:47
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If you talk to any professional worth their salt, they will tell you "there is more than 1 way to skin a cat"... All insulations (and wall assemblies in general) have pros and cons. There are good and bad installations of any and all systems.
I'm definitely not saying that what you did is wrong - it's a very good way to insulate, and definitely the path many are taking in the 21st century. Well applied, foam does 3 things at once: insulate, air seal, vapour seal. It also has a high R value per inch. If your pros did a good job, your home will indeed be very air tight and relatively vapour tight. That is what B. Millar is alluding to: if you seal a house tight, it *needs* adequate mechanical ventilation or you risk having poor indoor air quality. Any competent pro will tell you that. Not roof ventilation. Whole house ventilation (an HRV, ERV, or some other means of air exchange). Spraying foam directly under the roof sheathing is one method of achieving a "hot roof", which works perfectly well so long as 1) you spray enough foam thickness ($$) and 2) you don't mind potentially violating a clause in some shingle manufacturer's warranty (they often require ventilated sheathing to guarantee 25 years lifetime - the presumption that insulating the sheathing makes the roof hotter, and deteriorates shingles faster... but imho that is not really a big deal and roof lifetimes are mostly bogus anyway, so I wouldn't personally worry about that). Imho, a hot roof is a perfectly reasonable solution (done right).
In an old house, they did breathe through air leakage through every crack and gap in the walls, ceiling, sills, windows, etc and they were fine that way uninsulated, but not very energy efficient. Put some fiberglass in those walls without air + vapour sealing, and all of a sudden they start to rot (penetrating moisture condenses on the fibreglass). Most houses (even very new ones) have a big enough combined hole that you could throw a cat through it! It is much better to seal that up (eg with foam) and then provide a controlled ventilation source through a heat exchanger. However, all of that is not cheap. The reason I prefer cellulose for old homes, is it is very fault tolerant - it does not require perfect (or even good) vapour barriers to be effective and not cause rot. It has lower R/inch than foam, but still good, and high R/$ applied. There are downsides: eg it can settle, or have voids. But all in all, it is a relatively non-invasive way to make an old home significantly more energy efficient in a cold climate.
But if you only listen to the guy selling foam, or Mike Holmes (a guy paid to endorse foam), you'll only get their opinion... which is designed to sell you foam! Nothing wrong with that, but there is a bigger picture.
->Posting last edited on Wed, 19 Feb 2014 03:32:34.
, Tue, 18 Feb 2014 08:34:17, Thu, 20 Feb 2014 10:44:57, Thu, 20 Feb 2014 11:47:30, Thu, 20 Feb 2014 13:01:31, Wed, 19 Feb 2014 17:42:50, Tue, 18 Feb 2014 16:32:01, Tue, 18 Feb 2014 15:10:28, Tue, 18 Feb 2014 15:51:16, Tue, 18 Feb 2014 10:39:41, Tue, 18 Feb 2014 10:54:21, Tue, 18 Feb 2014 11:31:16, Tue, 18 Feb 2014 16:28:47, Wed, 19 Feb 2014 03:32:02 <-- Viewing This Message, Tue, 18 Feb 2014 09:06:31, Tue, 18 Feb 2014 10:26:00, Tue, 18 Feb 2014 11:22:16, Tue, 18 Feb 2014 11:56:11, Tue, 18 Feb 2014 11:49:38, Tue, 18 Feb 2014 08:56:05, Tue, 18 Feb 2014 15:57:52, Tue, 18 Feb 2014 16:41:42, Wed, 19 Feb 2014 09:29:53
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